Linux basics cheat-sheet

#resources/linux/basics

1. Basic Commands:

  • pwd: Prints the current working directory.
  • ls : Lists the files and directories in the current directory.
  • ls -l: Lists files in long format (with permissions, owner, etc.).
  • ls -a: Lists all files, including hidden ones.
  • cd [directory]: Changes the directory.
  • cd ..: Goes back to the previous directory (parent directory).
  • cd ~: Changes to the home directory.
  • cd - : return to Previous PATH/directory
  • mkdir [directory_name]: Creates a new directory.
  • rmdir [directory_name]: Removes an empty directory.
  • touch [file_name]: Creates an empty file or updates the modification time if the file exists.
  • cp [source][destination]: Copies a file or directory.
  • mv [source] [destination]: Moves or renames a file or directory.
  • rm [file_name]: Removes a file.
  • rm -r [directory_name]: Removes a directory and its contents recursively.
  • cat [file_name]: Displays the contents of a file.
  • nano [file_name]: Opens a file in the nano text editor.
  • clear: Clears the terminal screen.

2. System Information:

  • uname -a: Displays information about the system.
  • df -h: Shows disk space usage in human-readable format.
  • du -sh [directory]: Displays the disk usage of a directory.
  • top: Shows a real-time view of system processes and resource usage.
  • htop: An improved version of top (requires installation: sudo apt install htop).
  • free -h: Displays the amount of free and used memory in the system.
  • uptime: Shows how long the system has been running.
  • whoami: Prints the current logged-in username.
  • hostname: Displays the system's hostname.

3. File Permissions and Ownership:

  • chmod [permissions] [file]: Changes the file's permissions.
    • Example: chmod 755 file.sh gives the owner full permissions, and others read and execute permissions.
    • chmod +x [file]: Makes a file executable.
  • chown [user:group] [file]: Changes the file's ownership.
    • Example: chown user:user file.txt

4. Network:

  • ifconfig: Displays network interface configuration.
  • ip a: Shows IP address and network interfaces.
  • ping [domain]: Tests network connectivity to a domain or IP address.
  • curl [URL]: Downloads content from a URL.
  • wget [URL]: Another way to download files from a URL.
  • ssh [user]@[hostname]: Connects to a remote system via SSH.

5. Package Management (APT):

  • sudo apt update: Updates the package list.
  • sudo apt upgrade: Installs available updates.
  • sudo apt install [package_name]: Installs a package
  • sudo apt remove [package_name]: Removes a package.
  • sudo apt autoremove: Removes unnecessary packages.

6. Process Management:

  • ps aux: Lists running processes.
  • kill [PID]: Kills a process by its PID (Process ID).
  • killall [process_name]: Kills all instances of a specific process.
  • bg: Resumes a suspended job in the background.
  • fg: Brings a background job to the foreground.

7. User Management:

  • sudo adduser [username]: Adds a new user.
  • sudo deluser [username]: Deletes a user.
  • passwd [username]: Changes the password for a user.

8. Archiving and Compression:

  • tar -cvf archive.tar [files]: Creates a tar archive.
  • tar -xvf archive.tar: Extracts a tar archive.
  • gzip [file]: Compresses a file using gzip.
  • gunzip [file.gz]: Decompresses a gzip file.

9. Searching:

  • find [path] -name [file_name]: Finds a file by name.
  • grep '[pattern]' [file]: Searches for a pattern in a file.
    • Example: grep 'error' log.txt will search for the word 'error' in the log.txt file.

10. Permissions (Special Commands):

  • sudo [command]: Runs a command as the superuser (admin privileges).
  • su [username]: Switches to another user.

11. Disk Management:

  • fdisk -l: Lists all available partitions.
  • mount [device] [directory]: Mounts a device to a directory.
  • umount [device/directory]: Unmounts a device.

12. History and Shortcuts:

  • history: Displays the list of recently executed commands.
  • !!: Repeats the last command.
  • !n: Executes the nth command in history.
  • Ctrl + C: Stops the current command.
  • Ctrl + Z: Suspends the current command.
  • Ctrl + A: Moves the cursor to the beginning of the line.
  • Ctrl + E: Moves the cursor to the end of the line.

13. Other Commands:

• wget -c [URL]: Downloads a file from a URL and continues if interrupted.
• curl -O [URL]: Downloads a file from a URL.

14. File Compression and Decompression:

  • zip [archive.zip] [file1] [file2]: Creates a zip archive.
  • unzip [archive.zip]: Extracts a zip archive.
  • tar -cvzf archive.tar.gz [files]: Creates a gzipped tar archive.
  • tar -xvzf archive.tar.gz: Extracts a gzip

15. The Help (man && --help):

  • man stands for manual it helps you to view manual how to use the commands.
    • man command in Linux its useful in case no network connection*.
    • It is ideal for deep understanding or troubleshooting more complex command behavior. also It requires that manual pages are installed on the system.
  • The --help flag provides a quick, concise overview of a command's usage, available options, and syntax.
    • It is useful for fast reference when you need a basic understanding or want to quickly see available flags.
    • Not all commands support --help.

16. Difference Between Switch and Flag

#resources/linux/basics

  • Switch (-): Short, single-letter option.
    Example: ls -a → show hidden files.
  • Flag (--): Long, descriptive option.
    Example: ls --help → show help message.

Pasted image 20251003190224.png